<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        let num1 = 10000
         while(true){
             let change = prompt(`
             1.取款
             2.存钱
             3.查看余额
             4.退出`)
             switch(change){
                 case'取款':
                 let qukuan =+ prompt('请输入取款金额：')
                 num1-= qukuan;
                 break;
                 case'存钱':
                 let cunkuan =+ prompt('请输入存款金额：')
                 num1+=cunkuan;
                 break;
                 case'查看余额':
                 alert(num1);
                 break;
             }
             if(change=='退出'){
                 break;
             }
         }
    </script>
</body>
</html>